I'm just quoting this to make sure that people do see this on the 2nd page. Invest at your own risk!
If you are a newbie to Bitcoin and reading this, I'd like to shed some light on what all of these "Doublers" are. Simply put, they are Ponzi schemes. They rely on "investments" from new members in order to payout the previous members. Once the new suckers stop rolling in, they shut down their shop, and walk away with dozens, if not hundreds, of Bitcoins with them. The deception is carried out in three ways:
1. The site is professionally designed. Nowadays, you can buy HTML templates for $15-25 for a beautifully designed site that you can change and modify to fit your needs. Additionally, you can buy professionally-produced audio and video clips for $5 on Fiverr. Put all this together, with cheap shared hosting for 1 year (less than $25), and you have yourself a scammy website for less than $100.
2. They claim that they will invest your money into the coin markets and/or mining pools. Don't fall into this hype. If the coin markets were doing well, and one was able to earn a shitload of money from them, why the hell do they need your money? Think about it. If they can double YOUR bitcoin, why can't they double their own? If it takes only 4 days to double your bitcoin, within 2 months, 1BTC will net you over 30,000BTC. So why the hell are they asking you for YOUR investment? Seriously, think about it.
3. "But they paid me!" They always do. In the beginning. Why? Because they've just made a pawn out of you. Most of these HYIP's and Ponzis look at the amount of traffic that is going in and out of your BTC address, and if it's a considerable amount, they'll pay you your return! This is because they figure that if you have a high amount of traffic in your BTC wallet, that you're active in the BTC community. They're counting on you going out there and spreading the word about their "investment" platform to get more suckers. Don't fall victim to it. Chances that you are one of the ones to get paid, out of the dozens, hundreds, or thousands of victims are very slim.
With that said, if you join these types of sites, you're contributing to the fall of the Bitcoin industry. I don't care what the admin or developers of these sites say; EVERY SINGLE HYIP AND PONZI SITE IS A SCAM OR WILL BECOME ONE EVENTUALLY.
If you've read what I've written, and still decide to "invest", I pity you. You deserve to lose whatever you put into these sites.